FIG. 1 is a diagram of a heterogeneous network wireless communication system 100 including a macro base station and a micro base station. In this specification, a terminology of a heterogeneous network means a network in which the macro base station 110 and the micro base stations 121/122 co-exist although an identical Radio Access Technology (RAT) is used.
The macro base station 121 means a general base station of a wireless communication system having a wide coverage and high transmit power. The macro base station 110 may also be named a macro cell.
For instance, the micro base station 121/122 can be named a micro cell, a pico cell, a femto cell, a home eNB (HeNB), a relay, or the like. The micro base station 121/122 is a small version of the macro base station 110 and can operate independently in a manner of performing most of functions of the macro base station. The micro base station is a sort of base stations installed (overlay) in an area covered by the macro base station or the base stations installable (non-overlay) in a radio shadow area where the macro base station is not able to cover. Compared to the macro base station 110, the micro base station 121/122 can accommodate small numbers of user equipments with a narrower coverage and lower transmit power.
A user equipment (hereinafter called a macro UE) 131 may be directly served from the macro base station 110 and a user equipment (hereinafter called a micro UE) 132 may be served from the micro base station 122 as well. In some cases, the user equipment 132 existing in the coverage of the micro base station 122 may be served from the macro base station 110.
If a user equipment served by a macro base station is adjacent to a micro base station, a downlink signal, which is received by a macro user equipment from the macro base station, may be interfered by interference occurred due to a strong downlink signal from the micro base station. Or, a user equipment served by the micro base station may be significantly interfered by interference occurred due to a downlink signal of the macro base station. as mentioned in the foregoing description, if one cell is significantly interfered by a neighboring cell, inter-cell interference coordination (ICIC) for mitigating/eliminating interference can be performed in a manner that the neighboring cell restricts transmission of the neighboring cell in a part of resource regions (e.g., a part of subframes and/or a part of frequency bands).